Optical glass, glass preform or optical element made therefrom, and optical instrument

ABSTRACT

Disclosed are optical glass, a glass preform or an optical element made therefrom and an optical instrument. The optical glass is calculated by a mass percentage content relative to a total mass of glass converted by an oxide, and the optical glass includes: B 2 O 3 : 5˜25%, La 2 O 3 : 25˜45%, Gd 2 O 3 : 15˜35%, Y 2 O 3 : 0˜10%, Yb 2 O 3 : 0˜10%, Nb 2 O 5 : 2˜15%, SiO 2 : 0.5˜15%, ZrO 2 : 1˜15%, TiO 2 : 0.5˜10% and WO 3 : 0˜10%, a weight ratio of Nb 2 O 5  to TiO 2 , i.e., Nb 2 O 5 /TiO 2 , is 2.17˜8.5, and Ta 2 O 5  is not contained.

TECHNICAL FIELD

The disclosure relates to the technical field of optical glass, and inparticular to an optical glass, a glass preform or an optical elementmade therefrom and an optical instrument.

BACKGROUND

At present, along with the development of a digital camera device, acamera shooting device and a projection device and the like,requirements for an optical element are higher, this requires thedevelopment and production of optical glass with higher performance.Herein, a lens formed by high refractive index and low dispersionoptical glass is combined with a lens formed by high refractive indexand high dispersion optical glass, and a chromatic aberration may becorrected, so an optical system is miniaturized, especially the highrefractive index and low dispersion optical glass of which a refractiveindex nd is greater than 1.87 and an Abbe number vd is greater than38.0, a market demand is increased day by day.

In order to meet the above optical property indexes, it is better that abasic formula system is B—La—Zr—Ta, it is easy to form the glass andbeneficial to production, but Ta is expensive, it is not beneficial tothe control of a production cost. In addition, under normal conditions,it is necessary to introduce more rare earth oxides in a high refractiveindex and low dispersion glass formula system so as to improve arefractive index of the glass. However, in different formula systems,the more lanthanide oxides introduced may affect a glass formingability, the glass may easily be crystallized if a content is higher,and a upper crystallization temperature is higher, it bringsdifficulties to a mass production process manufacture.

SUMMARY

The disclosure aims to provide an optical glass, a glass preform or anoptical element made therefrom and an optical instrument, as to solvetechnical problems existing in the prior art that high refractive indexand low dispersion optical glass is easy in devitrification, difficultto mass production, and higher in cost.

In order to achieve the above purpose, according to one aspect of thedisclosure, an optical glass is provided. The optical glass iscalculated by a mass percentage content relative to a total mass ofglass converted by an oxide, and the optical glass includes: B₂O₃:5˜25%, La₂O₃: 25˜45%, Gd₂O₃: 15˜35%, Y₂O₃: 0˜10%, Yb₂O₃: 0˜10%, Nb₂O₅:2˜15%, SiO₂: 0.5˜15%, ZrO₂: 1˜15%, TiO₂: 0.5˜10% and WO₃: 0˜10%, aweight ratio of Nb₂O₅ to TiO₂, i.e., Nb₂O₅/TiO₂, is 2.17˜8.5, and Ta₂O₅is not contained.

Further, the sum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is 50˜75%, and the sumof TiO₂, Nb₂O₅ and WO₃ is 1˜20%.

Further, the optical glass further includes one or more selected from agroup consisting of ZnO, BaO, CaO, SrO, MgO, Sb₂O₃, Li₂O, Na₂O and K₂O,and the content is as follows: ZnO: 0˜15%, BaO: 0˜10%; CaO: 0˜10%; SrO:0˜10%; MgO: 0˜10%; Sb₂O₃: 0˜1%, the sum of Li₂O, Na₂O and K₂O is 0˜10%.

Further, relative to the total mass of the glass converted by the oxide,and calculated by the mass percentage content, the optical glass isconsisted of B₂O₃: 5˜25%, SiO₂: 0.5˜15%, ZrO₂: 1˜15%, ZnO: 0˜15%, BaO:0˜10%, CaO: 0˜10%, SrO: 0˜10%, MgO: 0˜10%, the sum of TiO₂, Nb₂O₅ andWO₃ is 1˜20%, the sum of Li₂O, Na₂O and K₂O is 0˜1%, Sb₂O₃: 0˜1%, andthe sum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is 50˜75%.

Further, relative to the total mass of the glass converted by the oxide,and calculated by the mass percentage content, the optical glassincludes: B₂O₃: 8˜22%, SiO₂: 3˜10%, ZrO₂: 3˜12%, the sum of TiO₂, Nb₂O₅and WO₃ is 5˜15%, and/or the sum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is55˜70%.

Further, the weight ratio of the Nb₂O₅ to SiO₂, i.e., Nb₂O₅/SiO₂, is0.75˜2, preferably 1˜1.5.

Further, a weight ratio of the La₂O₃ to Gd₂O₃, i.e., La₂O₃/Gd₂O₃, is1.28˜1.625, preferably the La₂O₃/Gd₂O₃ is 1.3˜1.6, and more preferably1.4˜1.5.

Further, the optical glass does not contain the Y₂O₃ and/or the WO₃.

Further, the weight ratio of the ZrO₂ to SiO₂, i.e., ZrO₂/SiO₂,≥1.

Further, a upper crystallization temperature of the optical glass islower than 1350° C., preferably lower than 1300° C.

Further, a refractive index of the optical glass nd>1.87, preferablynd>1.88; and an Abbe number vd>38.0, preferably vd>39.0.

Further, durability of water Dw of the optical glass is above grade 3,preferably above grade 2, more preferably grade 1; and durability ofacid D_(A) is above grade 3, preferably above grade 2, and morepreferably grade 1.

Further, a extent of striae of the optical glass is above grade C,preferably above grade B, and more preferably grade A; and a bubblecontent is above grade A, preferably above grade A₀, and more preferablygrade A₀₀.

Further, while a transmittance of the optical glass reaches 70%, acorresponding wavelength λ₇₀ is less than or equal to 420 nm, preferablyless than or equal to 390 nm; and while the glass transmittance reaches5%, a corresponding wavelength A₅ is less than or equal to 360 nm,preferably less than or equal to 350 nm.

Further, a density of the optical glass is less than 5.3 g/cm³,preferably less than 5.23 g/cm³.

According to another aspect of the disclosure, a glass preform or anoptical element is provided. The glass preform or the optical element ismade of any one of the above optical glass.

According to another aspect of the disclosure, an optical instrument isprovided, the optical instrument includes an optical element, and theoptical element is any one of the above optical elements.

By applying a technical solution of the disclosure, and strictlycontrolling components, a content and a dosage proportion betweenspecific components of the optical glass, the optical glass of thedisclosure may acquire the high refractive index and low dispersionoptical glass with devitrification resistance and excellent performancein the case without using the Ta₂O₅, and the optical glass of thedisclosure is low in production cost, and easy to mass production.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It is to be noted that embodiments in the present application andfeatures in the embodiments may be combined with each other in the casewithout conflicting. The disclosure is described in detail below incombination with the embodiments.

In the description, unless otherwise specified, contents of variouscomponents are all represented by mass % relative to a total mass ofglass converted by an oxide. Herein, “converted by an oxide” means thatit is assumed that raw materials as constituent components of the glassof the disclosure are all decomposed and converted into the oxidesduring melting, and a total mass of the generated oxides are used as 100mass % to represent various components contained in the glass.

A basic effect played by each component in the optical glass isdescribed below, but it does not improperly limit a synergistic effector an unexpected effect between the components due to a specific contentratio.

Glass Components

B₂O₃ is a framework component of the glass, and has effects of improvingglass meltability, devitrification resistance and reducing glassdispersion in the disclosure. However, while a content of B₂O₃ exceeds25%, the stability of the glass may be decreased, and the refractiveindex is decreased. While a content of B₂O₃ is less than 5%, the glassmeltability is decreased, and it fails to reach an optical constantrequired by the disclosure. Therefore, a content of B₂O₃ in thedisclosure is 5˜25%, and the content of B₂O₃ is preferably 8˜22%.

SiO₂ is a component for constituting a glass framework, and it haseffects of improving devitrification resistance and extending anoperating temperature range. In addition, it also has the effects ofimproving the chemical stability of the glass and improving the thermalstability of the glass and the like. If a content of SiO₂ exceeds 15%,the glass meltability may be decreased, and the refractive indexrequired by the disclosure may not be obtained. In the disclosure, thecontent of SiO₂ is 0.5˜15%, preferably the content of SiO₂ is 3˜10%.

ZrO₂ is a component for improving the refractive index and stability.Because it forms the glass as an intermediate oxide, it also has effectsof improving the devitrification resistance and chemical durability.While a content of ZrO₂ is less than 1%, the above expected effects maynot be achieved, and while the content of ZrO₂ exceeds 15%, there is atendency that the devitrification becomes stronger and the vitrificationbecomes more difficult. In the disclosure, the content of ZrO₂ is 1˜15%,and preferably the content of ZrO₂ is 3˜12%.

It is discovered through a research by the inventor that a beneficialeffect of density lightweight may also be brought by controllingZrO₂/SiO₂≥1. The ZrO₂/SiO₂ is preferably 3 or less, preferably 0.7˜2,and more preferably 1˜1.5.

TiO₂ also has an effect of improving the refractive index of the glass,and may participate in formation of a glass network, and an appropriatecontent of TiO₂ makes the glass more stable. However, if the content ofTiO₂ is excessive, the glass dispersion may be improved significantly,and at the same time, a transmittance of a short-wave part of a visiblelight region of the glass is decreased, and a tendency of coloring ofthe glass is increased. In the disclosure, a content of TiO₂ is 0.5˜10%,and preferably 0.5˜7%.

Nb₂O₅ is a component for improving the refractive index and dispersion,and also has effects of improving the devitrification resistance andchemical durability of the glass. The TiO₂ also has an effect ofimproving the refractive index of the glass, and may participate in theformation of the glass network, and an appropriate content of Nb₂O₅makes the glass more stable. WO₃ plays a role in improving therefractive index, and it is discovered through a research by theinventor that the sum of TiO₂, Nb₂O₅ and WO₃ in the disclosure iscontrolled to a range of 1˜20%, while the sum of TiO₂, Nb₂O₅ and WO₃ isless than 1%, the effects required by the disclosure are not achieved;and if the content of TiO₂, Nb₂O₅ and WO₃ exceeds 20%, the glassdispersion may be significantly improved, the transmittance of theshort-wave part of the visible light region of the glass may bedecreased, the coloring tendency is improved, and the optical propertyof the glass of the disclosure may not be achieved. In addition, theTiO₂, Nb₂O₅ and WO₃ are synergistic with other components to effectivelyreduce the density of the glass of the disclosure, the sum of TiO₂,Nb₂O₅ and WO₃ is preferably 5˜15%, and the WO₃ is preferably notcontained in the disclosure.

Ta₂O₅ is not included in the glass components of the disclosure, but thehigh refractive index and low dispersion may be achieved by adding Nb₂O₅or TiO₂, preferably the TiO₂ and Nb₂O₅ coexist as the glass components,more preferably the Nb₂O₅/TiO₂ is controlled to 2.17˜8.5, furtherpreferably the Nb₂O₅/TiO₂ is 3.8˜6.5, and more preferably the Nb₂O₅/TiO₂is 4˜5.5, and while a coloration degree of the glass is effectivelysuppressed, a upper crystallization temperature of the glass iseffectively reduced, and the glass stability is excellent.

La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ are all main components for improving therefractive index of the glass, may improve the refractive index, but maynot significantly improve the dispersion. A certain content of the aboverare earth oxides are added in the glass of the present application, sothe upper crystallization temperature may be reduced, thedevitrification resistance of the glass is improved, the chemicalstability is improved, and it is not easy to generate glass bubblesduring a melting process and the like. Therefore, in a formula system ofthe high refractive index and low dispersion glass of the disclosure,the sum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is not less than 50% and notmore than 75%, as to ensure the achievement of the above technicaleffects and achieve the purpose of the disclosure; and a preferred rangeis 55˜70%, more preferably 60-67%.

However, under normal conditions, introduction of more lanthanide oxidesmay also affect a glass forming ability. If a content is excessive, theglass is easy to crystallize, and the upper crystallization temperatureis higher, difficulties are brought to a mass production processmanufacture. Therefore, the content of the lanthanide oxides with thehigh refractive index and low dispersion performance is usually below60% to ensure that the glass is not easy to crystallize, and in the highrefractive index and low dispersion glass of the disclosure, throughcontrolling the components and a weight ratio of the lanthanide oxidesLa₂O₃ to Gd₂O₃, i.e., La₂O₃/Gd₂O₃, to be 1.28˜1.625, it still may beguaranteed that the upper crystallization temperature of the glass isnot improved while the content of the lanthanide oxides is less than 60%and more than 60%, the upper crystallization temperature is lower than1350° C., preferably lower than 1300° C., and more preferably lower than1280° C., it may be ensured that the glass forming abilities of thecomponents are better, the glass bubbles are not easily generated in themelting process, and good optical property and forming property are alsoguaranteed and the like. Preferably, the La₂O₃/Gd₂O₃ is 1.3˜1.6; andmore preferably, the La₂O₃/Gd₂O₃ is 1.4˜1.5.

ZnO may adjust the refractive index and dispersion of the glass, asuitable content of ZnO may achieve effects of improving the stabilityor meltability of the glass, and improving press formability. However,while a content thereof is too high, the refractive index is reduced,the requirements of the disclosure may not be achieved, and at the sametime, the devitrification resistance of the glass is decreased, and theupper crystallization temperature is improved. Therefore, the content ofZnO of the disclosure is 0˜15%, preferably 0˜10%, and more preferably0˜5%.

Alkaline earth metal oxides such as BaO, CaO, SrO, and MgO may reducethe chemical stability of the glass and improve the uppercrystallization temperature, but while a respective content thereofexceeds 10%, the devitrification resistance of the glass is reduced.Therefore, the content of BaO in the disclosure is 0˜10%; the content ofCaO is 0˜10%; the content of SrO is 0˜10%, and the content of MgO is0˜10%.

Li₂O, Na₂O, and K₂O are components for suppressing phase separation andimproving glass stability. While a content thereof exceeds 10%, there isa tendency that the chemical stability is significantly reduced or therefractive index is reduced. Preferably, the sum of Li₂O, Na₂O and K₂Ois 0˜10%.

According to a typical implementation mode of the disclosure, an opticalglass is provided. The optical glass is calculated by a mass percentagecontent relative to a total mass of glass converted by an oxide, and theoptical glass includes: B₂O₃: 5˜25%, La₂O₃: 25˜45%, Gd₂O₃: 15˜35%, Y₂O₃:0˜10%, Yb₂O₃: 0˜10%, Nb₂O₅: 2˜15%, SiO₂: 0.5˜15%, ZrO₂: 1˜15%, TiO₂:0.5˜10% and WO₃: 0˜10%, a weight ratio of Nb₂O₅ to TiO₂, i.e.,Nb₂O₅/TiO₂, is 2.17˜8.5, and Ta₂O₅ is not contained.

By applying a technical solution of the disclosure, and strictlycontrolling components, a content and a dosage proportion betweenspecific components of the optical glass, the optical glass of thedisclosure has good devitrification resistance and optical performancein the case without using the Ta₂O₅, and is easy to mass production andlow in production cost.

According to a typical implementation mode of the disclosure, theoptical glass further includes one or more selected from a groupconsisting of ZnO, BaO, CaO, SrO, MgO, Sb₂O₃, Li₂O, Na₂O and K₂O, andthe content is as follows: ZnO: 0˜15%, BaO: 0˜10%; CaO: 0˜10%; SrO:0˜10%; MgO: 0˜10%; Sb₂O₃: 0˜1%, the sum of Li₂O, Na₂O and K₂O is 0˜10%.

According to a typical implementation mode of the disclosure, relativeto the total mass of the glass converted by the oxide, and calculated bythe mass percentage content, the optical glass consists of B₂O₃: 5˜25%,SiO₂: 0.5˜15%, ZrO₂: 1˜15%, ZnO: 0˜15%, BaO: 0˜10%, CaO: 0˜10%, SrO:0˜10%, MgO: 0˜10%, the sum of TiO₂, Nb₂O₅ and WO₃ of is 1˜20%, the sumof Li₂O, Na₂O and K₂O is 0˜1%, Sb₂O₃: 0˜1%, and the sum of La₂O₃, Gd₂O₃,Y₂O₃ and Yb₂O₃ is 50˜75%. Herein, a weight ratio of La₂O₃ to Gd₂O₃,i.e., La₂O₃/Gd₂O₃, is 1.28˜1.625. The components, the content and thedosage proportion between the specific components of the optical glassare strictly controlled, so that the optical glass of the disclosure hasthe better devitrification resistance and the good optical property inthe case without using the Ta₂O₅, and is easy to mass production and lowin production cost.

Preferably, according to a typical implementation mode of thedisclosure, relative to the total mass of the glass converted by theoxide, and calculated by the mass percentage content, the optical glassincludes: B₂O₃: 8˜22%, SiO₂: 3˜10%, ZrO₂: 3˜12%, the sum of TiO₂, Nb₂O₅and WO₃ is 5˜15%, and/or the sum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is55˜70%.

In the disclosure, the Y₂O₃ may improve meltability and devitrificationresistance of the glass, and at the same time may reduce a uppercrystallization temperature of the glass, but if a content thereofexceeds a certain amount, the stability and devitrification resistanceof the glass is decreased. The WO₃ plays a role in improving therefractive index, but while a WO₃ content exceeds 10%, there is atendency of enhanced devitrification and difficult vitrification, thedispersion is significantly improved, a transmittance at ashort-wavelength side of a visible light region of the glass isdecreased, and a tendency of coloring is improved. Therefore, thecontent of WO₃ is preferably 0˜10% in the disclosure. According to atypical implementation mode of the disclosure, the optical glasspreferably does not contain the Y₂O₃ and/or the WO₃.

In the disclosure, through controlling a ratio of Nb₂O₅ to SiO₂, i.e.,Nb₂O₅/SiO₂, to be within 0.75˜2, not only the meltability of the glassmay be improved, but also the stability of the glass is effectivelyimproved, it is not easy to generate a strip, a glass uniformity isgood, and it has effects of improving the refractive index, thecrystallization resistance and the chemical durability of the glass inthe case without deteriorating the transmittance, especially while theratio of Nb₂O₅/SiO₂ is 1˜1.5, the effect is particularly apparent.

A clarification effect of the glass may be improved by adding a smallamount of Sb₂O₃, SnO₂, and CeO₂ components. However, while a content ofSb₂O₃ exceeds 1%, the glass has a tendency of reducing the clarificationperformance, and at the same time, because a strong oxidation effectthereof promotes deterioration of a forming mold, an addition amount ofthe Sb₂O₃ is preferably is 0˜1% in the disclosure, and more preferably0˜0.5%. The SnO₂ may also be added as a clarifying agent, but while acontent thereof exceeds 1%, the glass may be colored, or while the glassis formed again by heating, softening and molding and the like, Sn maybecome a starting point for generation of a crystal nucleus, and atendency of the devitrification is generated. Therefore, the content ofSnO₂ in the disclosure is preferably 0˜1%, more preferably 0˜0.5%, andfurther preferably it is not added. An effect and an addition proportionof CeO₂ are the same as the SnO₂, and a content thereof is preferably0˜1%, more preferably 0˜0.5%, and further preferably it is not added.

Under a precondition without affecting the performance of the opticalglass of the disclosure, a certain amount of P₂O₅, Al₂O₃, Bi₂O₃, GeO₂,Lu₂O₃, F and other components may be appropriately introduced.

The optical glass of the disclosure is the high refractive index and lowdispersion glass, a lens made of the high refractive index and lowdispersion glass is mostly combined with a lens made of the highrefractive index and high dispersion glass for chromatic aberrationcorrection, and in the case that the optical glass is used as a lens,the refractive index is higher, the lens may be thinner, and it isbeneficial to miniaturization of an optical device. The refractive indexof the optical glass of the disclosure nd>1.87, preferably nd>1.88, anAbbe number vd>38.0, preferably vd>39.0.

In manufacture and use processes of an optical glass element, an abilityof a polished surface thereof to resist the action of various corrosivemediums such as water and acids is called as the chemical stability ofthe optical glass, and it is mainly dependent on chemical constituentsof the glass. Durability of water Dw (powder method) of the opticalglass of the disclosure is above grade 3, preferably above grade 2, andmore preferably grade 1; and durability of acid D_(A) (powder method) isabove grade 3, preferably above grade 2, and more preferably grade 1.The crystallization performance of the glass is measured by using atemperature gradient furnace method, the glass is made into a sample of180*10*10 mm, a side face is polished, and it is placed in a furnacewith a temperature gradient (5° C./cm). After a temperature is raised to1400° C. for 4 hours, it is taken out and naturally cooled to a roomtemperature. A devitrification condition of the glass is observed undera microscope, the highest temperature corresponding to the appearance ofa crystal in the glass is the upper crystallization temperature of theglass. The upper crystallization temperature of the glass is lower, thestability of the glass is stronger at a high temperature and the processperformance of production is better. According to a typicalimplementation mode of the disclosure, preferably, the uppercrystallization temperature of the optical glass is lower than 1350° C.,preferably lower than 1300° C., and more preferably lower than 1280° C.

The short-wave transmission spectrum property of the glass of thedisclosure is represented by a coloration degree (λ₇₀/λ₅). The λ₇₀refers to a wavelength corresponding to the glass transmittance of 70%,and the λ₅ refers to a wavelength corresponding to the glasstransmittance of 5%, Wherein, the measurement of the λ₇₀ is that glasshaving two mutually parallel and optically polished opposite planes witha thickness of 10±0.1 mm is used to measure a spectral transmittance ina wavelength range from 280 nm to 700 nm and a wavelength that shows 70%of the transmittance. The so-called spectral transmittance ortransmittance refers to an amount represented by I_(out)/I_(in) in thecase where a light having an incident intensity of I_(in) isperpendicularly incident to the surface of the glass, directed throughthe glass and a light having an incident intensity of I_(out) intensityis emergent from the other plane. and the amount also includes atransmittance of surface reflection loss on the surface of the glass.The higher the refractive index of the glass, the greater the surfacereflection loss. Accordingly, in the glass having a high refractiveindex, a small value of λ₇₀ means that the coloration of the glassitself is minimal. While the optical glass transmittance of thedisclosure reaches 70%, the corresponding wavelength (λ₇₀) λ₇₀ is lessthan or equal to 420 nm, preferably less than or equal to 390 nm. Whilethe glass transmittance thereof reaches 5%, the corresponding wavelength(λ₅) is less than or equal to 360 nm, preferably less than or equal to350 nm.

The density of the optical glass is a mass per unit volume at atemperature of 20° C., and a unit is represented by g/cm³. The densityof the optical glass of the disclosure is less than 5.3, preferably lessthan 5.23.

A extent of striae is detected by using a extent of striae instrumentformed by a point light source and a lens from a direction in which astripe is most easily seen. Compared with a standard sample, it isdivided into 4 grades, namely the grades A, B, C, and D. The grade Ameans that there are no macroscopic stripes under specified detectionconditions, the grade B means that there are thin and scattered stripesunder the specified detection conditions, the grade C means that thereare no slight parallel stripes under the specified detection conditions,and the grade D means that there are rough stripes under the specifieddetection conditions. Because this type of products in the prior art areworse in crystallization resistance under a condition without usingprecious oxides such as Ta₂O₅, the production of a product with athickness of more than 20 mm is easy to generate a devitrificationstripe. A thick specification product is a necessary specification formanufacturing a large-diameter (greater than 60 mm) lens. At present,due to the development of an optical technology, more and morelarge-diameter lenses are required, and manufacturers are required toprovide blank products with a thickness of more than 20 mm.

Bubble quality of the optical glass is measured according to a testmethod specified in GB/T 7962.8-2010. A bubble content is a level ofallowable bubble content in the glass. Bubbles may not only affect theappearance quality of a glass product, but also affect the opticalproperty, transparency, and mechanical strength and the like of theglass, and many adverse effects are caused to the glass. Therefore, itis very important to control the bubble content of the glass. In thedisclosure, through controlling the sum of rare earth oxides La₂O₃,Gd₂O₃, Y₂O₃ and Yb₂O₃, the bubble content of the glass may be furtherachieved above grade A, preferably above grade A₀, and more preferablygrade A₀₀.

According to another aspect of the disclosure, a glass preform or anoptical element is provided. The glass preform or the optical element ismade of any one of the above optical glass. The glass preform of thedisclosure has the characteristics of high refractive index and lowdispersion; and the optical element of the disclosure has thecharacteristics of high refractive index and low dispersion, and mayprovide various lenses, prisms and other optical elements with excellentoptical performance in low costs. In examples as the lenses, variouslenses such as a concave meniscus lens, a convex meniscus lens, abiconvex lens, a biconcave lens, a planoconvex lens and a planoconcavelens of which a lens surface is spherical or non-spherical may belisted. This types of the lens may correct chromatic aberration bycombining with a lens made of the high refractive index and highdispersion glass, and is suitably served as a lens for chromaticaberration correction. In addition, it is also an effective lens formaking the optical system compact. In addition, because of a highrefractive index, the prism faces to a required direction by combiningin a camera shooting optical system and bending an optical path, and acompact and wide-angle optical system may be achieved.

According to another aspect of the disclosure, an optical instrument isprovided, the optical instrument includes an optical element, and theoptical element is any one of the above optical elements. The opticalinstrument of the disclosure may be a digital camera, a video camera andthe like.

The beneficial effects of the disclosure are further described below incombination with embodiments.

Embodiment Embodiment of Optical Glass

In order to obtain glass having components shown in Table 1 to Table 9,a carbonate, a nitrate, a hydroxide, an oxide, a boric acid and the likeare used as raw materials, and raw materials corresponding to theoptical glass components are weighed in proportion. After beingadequately mixed, it becomes a blended raw material. The blended rawmaterial is put into a platinum crucible, and heated to 1200˜1450° C.After melting, stirring and clarifying, uniform molten glass is formed,and then the molten glass is poured into a preheated mold after beingmoderately cooled and kept at 650˜700° C. for 2˜4 hours, and then slowlycooled, to obtain the optical glass. In addition, the characteristics ofeach glass are measured by a method shown below, and measurement resultsare shown in Tables 1 to Table 9.

(1) Upper Crystallization Temperature

The crystallization performance of the glass is measured by using atemperature gradient furnace method, the glass is made into a sample of180*10*10 mm, a side face is polished, and it is placed in a furnacewith a temperature gradient (5° C./cm). After a temperature is raised to1400° C. for 4 hours, it is taken out and naturally cooled to a roomtemperature. A devitrification condition of the glass is observed undera microscope, the highest temperature corresponding to the appearance ofa crystal in the glass is the upper crystallization temperature of theglass.

(2) Refractive Index Nd and Abbe Number Vd

Refractive index and dispersion coefficient are tested according to amethod specified in GB/T7962.1-2010.

(3) Chemical Stability

Durability of water Dw and durability of acid D_(A) are tested accordingto a test method of GB/T 17129.

(4) Extent of Striae

It is measured according to a method specified in MLL-G-174B.

(5) Bubble Content

Bubble quality of the optical glass is measured according to a testmethod specified in GB/T7962.8-2010.

(6) Glass Coloration Degree (λ₇₀, λ₅)

A glass sample having two optically polished opposite planes with athickness of 10±0.1 mm is used to measure a spectral transmittance, andthe glass coloration degree is calculated according to a result thereof.

(7) Density

It is measured according to a method specified in GB/T7962.20-2010.

TABLE 1 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 1 2 3 4 5 6 7 B₂O₃ 15.1 13.9 12.9 167.5 13.3 16.6 Nb₂O₅ 8.5 7.4 7.3 6.7 5.6 4.2 6.7 SiO₂ 6.2 3.8 4.5 5.9 3 55.8 ZrO₂ 5.9 6 4 5.8 8.3 6.5 5.8 TiO₂ 1.5 0.9 1.5 1.5 0.6 2 3 La₂O₃ 3736 27.8 34 40 30 34 Gd₂O₃ 25.8 25.4 16.8 26 35 22 25.8 Y₂O₃ 0 0 0 0 0 90 Yb₂O₃ 0 0 8 0 0 8 0 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 BaO 0 0 81.5 0 0 0 CaO 0 2 0 2.6 0 0 0 SrO 0 0 0 0 0 0 0 MgO 0 0 0 0 0 0 2.2 WO₃0 0 0 0 0 0 0 Sb₂O₃ 0 0 0 0 0 0 0.1 Li₂O 0 3.5 4.5 0 0 0 0 Na₂O 0 1.14.7 0 0 0 0 K₂O 0 0 0 0 0 0 0 La₂O₃/Gd₂O₃ 1.434109 1.417323 1.6547621.307692 1.142857 1.363636 1.317829 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 62.861.4 52.6 60 75 69 59.8 Nb₂O₅/SiO₂ 1.370968 1.947368 1.622222 1.1355931.866667 0.84 1.155172 Li₂O + Na₂O + K₂O 0 4.6 9.2 0 0 0 0 TiO₂ +Nb₂O₅ + WO₃ 10 8.3 8.8 8.2 6.2 6.2 9.7 ZrO₂/SiO₂ 0.951613 1.5789470.888889 0.983051 2.766667 1.3 1 Nb₂O₅/TiO₂ 5.666667 8.222222 4.8666674.466667 9.333333 2.1 2.233333 Total content 100 100 100 100 100 100 100Upper crystallization 1280 1290 1350 1300 1350 1310 1300 temperature °C. Refractive index nd 1.882 1.888 1.875 1.885 1.879 1.887 1.878 Abbenumber vd 39.25 39.25 38.5 39.21 38.77 39.1 39.25 Durability of water Dw1 1 3 1 3 3 2 Durability of acid D_(A) 1 1 3 1 3 3 2 Density g/cm³ 5.275.28 5.30 5.27 5.30 5.17 5.18 λ₇₀ (nm) 395 390 400 384 387 375 380 λ₅(nm) 355 350 350 346 350 340 340 Extent of striae A B C A C C A Bubblecontent    A₀₀    A₀₀ B   A₀ A   A₀   A₀

TABLE 2 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 8 9 10 11 12 13 14 B₂O₃ 11.8 16 11.615 15.1 13.4 11.2 Nb₂O₅ 2 6.7 6.5 7.6 7.5 7.7 8 SiO₂ 1 5.9 4 6 5.8 6.15.7 ZrO₂ 3 5.8 2.8 6 6.1 6.2 6.4 TiO₂ 5 3 2.6 1.8 1.7 1.8 1.9 La₂O₃ 4334 25.8 38.2 38.5 38.8 39 Gd₂O₃ 30 26 15.9 25.4 24 26 27.8 Y₂O₃ 0 0 10 00 0 0 Yb₂O₃ 0 0 0 0 0 0 0 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 0 0 15 0 0 0 0 BaO 0 00 0 1.3 0 0 CaO 0 0 0 0 0 0 0 SrO 4.2 0 2 0 0 0 0 MgO 0 2.6 3.8 0 0 0 0WO₃ 0 0 0 0 0 0 0 Sb₂O₃ 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 0 0 Na₂O 0 0 0 0 00 0 K₂O 0 0 0 0 0 0 0 La₂O₃/Gd₂O₃ 1.433333 1.307692 1.622642 1.5039371.604167 1.492308 1.402878 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 73 60 51.7 63.662.5 64.8 66.8 Nb₂O₅/SiO₂ 2 1.135593 1.625 1.266667 1.293103 1.2622951.403509 Li₂O + Na₂O + K₂O 0 0 0 0 0 0 0 TiO₂ + Nb₂O₅ + WO₃ 7 9.7 9.19.4 9.2 9.5 9.9 ZrO₂/SiO₂ 3 0.983051 0.7 1 1.051724 1.016393 1.122807Nb₂O₅/TiO₂ 0.4 2.233333 2.5 4.222222 4.411765 4.277778 4.210526 Totalcontent 100 100 100 100 100 100 100 Upper crystallization 1320 1300 13501275 1290 1275 1275 temperature ° C. Refractive index nd 1.873 1.8831.872 1.886 1.883 1.884 1.887 Abbe number vd 39 39.25 38.8 39.35 39.3139.28 39.26 Durability of water Dw 2 1 3 1 1 1 1 Durability of acidD_(A) 2 1 3 1 1 1 1 Density g/cm³ 5.25 5.23 5.22 5.18 5.17 5.21 5.18 λ₇₀(nm) 390 375 380 376 375 380 385 λ₅ (nm) 350 340 340 340 340 345 345Extent of striae C B C A A A A Bubble content   A₀   A₀ A    A₀₀   A₀   A₀₀    A₀₀

TABLE 3 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 15 16 17 18 19 20 21 B₂O₃ 11.8 16 514.1 16 10.2 7.8 Nb₂O₅ 2 9.3 9.5 7.5 6.7 2.5 3.6 SiO₂ 1 8.5 10 5.8 5.91.3 2 ZrO₂ 7.2 1.5 0.5 6.1 5.8 3.8 5.7 TiO₂ 5 6.4 8 2.7 3 0.5 3.5 La₂O₃43 34.3 41 38.5 34 39 32.4 Gd₂O₃ 30 24 26 24 26 27.8 20 Y₂O₃ 0 0 0 0 0 00 Yb₂O₃ 0 0 0 0 0 0 0 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 11.2 4 BaO 0 0 00 0 2 8 CaO 0 0 0 0 0 0 6 SrO 0 0 0 0 0 0 7 MgO 0 0 0 1.3 2.6 0 0 WO₃ 00 0 0 0 0 0 Sb₂O₃ 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 1 0 Na₂O 0 0 0 0 0 0.7 0K₂O 0 0 0 0 0 0 0 La₂O₃/Gd₂O₃ 1.433333 1.429167 1.576923 1.6041671.307692 1.402878 1.62 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 73 58.3 67 62.5 6066.8 52.4 Nb₂O₅/SiO₂ 2 1.094118 0.95 1.293103 1.135593 1.923077 1.8Li₂O + Na₂O + K₂O 0 0 0 0 0 1.7 0 TiO₂ + Nb₂O₅ + WO₃ 7 15.7 17.5 10.29.7 3 7.1 ZrO₂/SiO₂ 7.2 0.176471 0.05 1.051724 0.983051 2.923077 2.85Nb₂O₅/TiO₂ 0.4 1.453125 1.1875 2.777778 2.233333 5 1.028571 Totalcontent 100 100 100 100 100 100 100 Upper crystallization 1320 1300 13201280 1290 1280 1360 temperature ° C. Refractive index nd 1.873 1.8811.883 1.886 1.885 1.882 1.878 Abbe number vd 39 39.1 39.1 39.31 39.339.26 38.25 Durability of water Dw 2 1 2 1 1 1 3 Durability of acidD_(A) 2 1 2 1 1 1 3 Density g/cm³ 5.25 5.25 5.26 5.28 5.24 5.28 5.24 λ₇₀(nm) 390 395 400 375 380 415 390 λ₅ (nm) 350 360 355 340 340 360 350Extent of striae C A B A A B B Bubble content   A₀    A₀₀   A₀   A₀   A₀₀    A₀₀ A

TABLE 4 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 22 23 24 25 26 27 28 B₂O₃ 7.5 8 5 5 613.3 7.8 Nb₂O₅ 5.6 6 9 9.7 10 4.2 3.6 SiO₂ 3 3.5 9 13 5 5 2 ZrO₂ 8.3 6.41.5 14 2.4 6.5 8.7 TiO₂ 0.6 0.8 1 1.3 1.6 2 3.5 La₂O₃ 40 41.3 42.5 35 4530 32.4 Gd₂O₃ 35 34 32 22 30 22 20 Y₂O₃ 0 0 0 0 0 9 0 Yb₂O₃ 0 0 0 0 0 80 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 2 BaO 0 0 0 0 0 0 7 CaO 0 0 0 0 00 5 SrO 0 0 0 0 0 0 8 MgO 0 0 0 0 0 0 0 WO₃ 0 0 0 0 0 0 0 Sb₂O₃ 0 0 0 00 0 0 Li₂O 0 0 0 0 0 0 0 Na₂O 0 0 0 0 0 0 0 K₂O 0 0 0 0 0 0 0La₂O₃/Gd₂O₃ 1.142857 1.214706 1.328125 1.590909 1.5 1.363636 1.62La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 75 75.3 74.5 57 75 69 52.4 Nb₂O₅/SiO₂1.866667 1.714286 1 0.746154 2 0.84 1.8 Li₂O + Na₂O + K₂O 0 0 0 0 0 0 0TiO₂ + Nb₂O₅ + WO₃ 6.2 6.8 10 11 11.6 6.2 7.1 ZrO₂/SiO₂ 2.7666671.828571 0.166667 1.076923 0.48 1.3 4.35 Nb₂O₅/TiO₂ 9.333333 7.5 97.461538 6.25 2.1 1.028571 Total content 100 100 100 100 100 100 100Upper crystallization 1360 1360 1350 1300 1290 1330 1360 temperature °C. Refractive index nd 1.879 1.878 1.883 1.883 1.884 1.885 1.878 Abbenumber vd 39.05 39.01 39.05 39.14 39.1 39.1 38.25 Durability of water Dw3 3 2 2 2 2 3 Durability of acid D_(A) 3 3 2 2 2 2 3 Density g/cm³ 5.275.28 5.24 5.18 5.24 5.2 5.25 λ₇₀ (nm) 375 380 390 380 380 380 390 λ₅(nm) 340 340 350 340 340 340 350 Extent of striae C C A B C C B Bubblecontent B B   A₀   A₀   A₀    A₀₀ A

TABLE 5 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 29 30 31 32 33 34 35 B₂O₃ 12.4 10.2 2216.6 15.9 12 12.4 Nb₂O₅ 6 8.3 5.6 6.7 6.6 7.4 6.5 SiO₂ 7.8 5.5 4 5.8 5.73.8 4 ZrO₂ 6.2 6 3.5 5.8 5.6 6 3 TiO₂ 2.8 2.9 2.5 3 3 2.8 2.4 La₂O₃ 38.839 37 34 35 32 25 Gd₂O₃ 26 27.8 25.4 25.8 26 24 15.9 Y₂O₃ 0 0 0 0 0 0 10Yb₂O₃ 0 0 0 0 0 3 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 15 BaO 0 0 0 0 00.4 1.8 CaO 0 0 0 2.2 1.9 1 SrO 0 0 0 0 0 0 0 MgO 0 0 0 0 0 0 0 WO₃ 0 00 0 0 0 0 Sb₂O₃ 0 0 0 0.1 0.1 0.1 0 Li₂O 0 0.3 0 0 0 3.5 0 Na₂O 0 0 0 00 1.1 0 K₂O 0 0 0 0 2.1 5 0 La₂O₃/Gd₂O₃ 1.492308 1.402878 1.4566931.317829 1.346154 1.333333 1.572327 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 64.866.8 62.4 59.8 61 56 53.9 Nb₂O₅/SiO₂ 0.769231 1.509091 1.4 1.1551721.157895 1.947368 1.625 Li₂O + Na₂O + K₂O 0 0.3 0 0 2.1 9.6 0 TiO₂ +Nb₂O₅ + WO₃ 8.8 11.2 8.1 9.7 9.6 10.2 8.9 ZrO₂/SiO₂ 0.794872 1.0909090.875 1 0.982456 1.578947 0.75 Nb₂O₅/TiO₂ 2.142857 2.862069 2.242.233333 2.2 2.642857 2.708333 Total content 100 100 100 100 100 100 100Upper crystallization 1280 1290 1250 1310 1280 1320 1310 temperature °C. Refractive index nd 1.883 1.886 1.882 1.88 1.884 1.883 1.885 Abbenumber vd 39.27 39.33 39.19 39.25 39.2 39.08 39.2 Durability of water Dw1 1 1 2 2 2 2 Durability of acid D_(A) 1 1 1 2 2 2 2 Density g/cm³ 5.305.19 5.30 5.17 5.24 5.24 5.26 λ₇₀ (nm) 380 390 375 380 375 390 390 λ₅(nm) 340 350 340 340 340 350 350 Extent of striae B B A A A C B Bubblecontent    A₀₀    A₀₀    A₀₀   A₀    A₀₀   A₀   A₀

TABLE 6 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 36 37 38 39 40 41 42 B₂O₃ 12.4 10.211.1 5.7 5 12.4 14.1 Nb₂O₅ 4.2 2.5 10 13 15 7.6 7.5 SiO₂ 6.1 1.3 6.2 5.93.1 7.6 5.8 ZrO₂ 6.2 7.5 5.9 5.8 3.8 6 6.1 TiO₂ 0.8 0.5 4 7 10 2.8 2.7La₂O₃ 38.8 39 37 34 35 38.2 38.5 Gd₂O₃ 26 27.8 25.8 26 26 25.4 24 Y₂O₃5.5 0 0 0 0 0 0 Yb₂O₃ 0 0 0 0 0 0 0 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 0 11.2 0 0 00 0 BaO 0 0 0 0 0 0 1.3 CaO 0 0 0 2.6 0 0 0 SrO 0 0 0 0 0 0 0 MgO 0 0 00 0 0 0 WO₃ 0 0 0 0 0 0 0 Sb₂O₃ 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 0 0 Na₂O 00 0 0 0 0 0 K₂O 0 0 0 0 2.1 0 0 La₂O₃/Gd₂O₃ 1.492308 1.402878 1.4341091.307692 1.346154 1.503937 1.604167 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 70.366.8 62.8 60 61 63.6 62.5 Nb₂O₅/SiO₂ 0.688525 1.923077 1.612903 2.203394.83871 1 1.293103 Li₂O + Na₂O + K₂O 0 0 0 0 2.1 0 0 TiO₂ + Nb₂O₅ + WO₃5 3 14 20 25 10.4 10.2 ZrO₂/SiO₂ 1.016393 5.769231 0.951613 0.9830511.225806 0.789474 1.051724 Nb₂O₅/TiO₂ 5.25 5 2.5 1.857143 1.5 2.7142862.777778 Total content 100 100 100 100 100 100 100 Upper crystallization1300 1280 1300 1320 1350 1300 1290 temperature ° C. Refractive index nd1.886 1.882 1.883 1.882 1.881 1.887 1.884 Abbe number vd 39 39.26 39.138.33 38.25 39.23 39.25 Durability of water Dw 2 1 2 2 2 1 1 Durabilityof acid D_(A) 2 1 2 2 2 1 1 Density g/cm³ 5.27 5.28 5.24 5.24 5.25 5.285.16 λ₇₀ (nm) 410 415 380 400 410 375 380 λ₅ (nm) 360 360 340 360 360340 340 Extent of striae D B B D D A A Bubble content   A₀    A₀₀    A₀₀  A₀   A₀    A₀₀    A₀₀

TABLE 7 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 43 44 45 46 47 48 49 B₂O₃ 11.6 12.9 1616.6 16 14 14.1 Nb₂O₅ 6.5 7.3 7.4 6.7 6.7 5.6 6 SiO₂ 4 4.5 3.8 5.8 5.9 65.8 ZrO₂ 2.8 4 6 5.8 5.8 6 6.1 TiO₂ 2.6 3 2.8 3 3 2.2 1.9 La₂O₃ 25.827.8 32 33.5 34 38.2 38.5 Gd₂O₃ 15.9 16.8 25.4 26 26 25.4 24 Y₂O₃ 10 0 00 0 0 0 Yb₂O₃ 0 8 0 0 0 0 0 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 15 0 0 0 0 0 0 BaO 08 0 0 0 0 1.3 CaO 3.8 0 2 2.6 2.6 0 0 SrO 2 0 0 0 0 0 2.3 MgO 0 0 0 0 00 0 WO₃ 0 0 0 0 0 2.6 0 Sb₂O₃ 0 0 0 0 0 0 0 Li₂O 0 3 3.5 0 0 0 0 Na₂O 04.7 1.1 0 0 0 0 K₂O 0 0 0 0 0 0 0 La₂O₃/Gd₂O₃ 1.622642 1.654762 1.2598431.288462 1.307692 1.503937 1.604167 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 51.752.6 57.4 59.5 60 63.6 62.5 Nb₂O₅/SiO₂ 1.625 1.622222 1.947368 1.1551721.135593 0.933333 1.034483 Li₂O + Na₂O + K₂O 0 7.7 4.6 0 0 0 0 TiO₂ +Nb₂O₅ + WO₃ 9.1 10.3 10.2 9.7 9.7 10.4 7.9 ZrO₂/SiO₂ 0.7 0.8888891.578947 1 0.983051 1 1.051724 Nb₂O₅/TiO₂ 2.5 2.433333 2.642857 2.2333332.233333 2.545455 3.157895 Total content 100 100 100 100 100 100 100Upper crystallization 1350 1360 1370 1300 1290 1280 1290 temperature °C. Refractive index nd 1.881 1.874 1.876 1.883 1.887 1.885 1.886 Abbenumber vd 38.8 38.5 38.7 39.12 39.23 39.25 39.21 Durability of water Dw3 3 3 1 1 1 1 Durability of acid D_(A) 3 3 3 1 1 1 1 Density g/cm³ 5.245.30 5.27 5.28 5.30 5.17 5.25 λ₇₀ (nm) 380 400 390 380 375 380 375 λ₅(nm) 340 350 350 340 335 340 340 Extent of striae C C C A A C A Bubblecontent A B B A    A₀₀   A₀   A₀

TABLE 8 Embodiment Embodiment Embodiment Embodiment EmbodimentEmbodiment Embodiment Component % 50 51 52 53 54 55 56 B₂O₃ 12.4 10.214.1 16 16 12 12.4 Nb₂O₅ 7.7 8 8.5 6.7 6.6 7.4 7.7 SiO₂ 6.1 5.7 6.2 5.95.7 3.8 6.1 ZrO₂ 6.2 6.4 5.9 5.8 5.6 6 6.2 TiO₂ 2.8 2.9 2.5 3 3 2.8 2.8La₂O₃ 38.8 39 37 34 35 36 38.8 Gd₂O₃ 26 27.8 25.8 26 26 25.4 26 Y₂O₃ 0 00 0 0 0 0 Yb₂O₃ 0 0 0 0 0 0 0 Ta₂O₅ 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 BaO0 0 0 0 0 0 0 CaO 0 0 0 2.6 0 2 0 SrO 0 0 0 0 0 0 0 MgO 0 0 0 0 0 0 0WO₃ 0 0 0 0 0 0 0 Sb₂O₃ 0 0 0 0 0 0 0 Li₂O 0 0 0 0 0 3.5 0 Na₂O 0 0 0 00 1.1 0 K₂O 0 0 0 2.1 0 0 La₂O₃/Gd₂O₃ 1.492308 1.402878 1.4341091.307692 1.346154 1.417323 1.492308 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 64.866.8 62.8 60 61 61.4 64.8 Nb₂O₅/SiO₂ 1.262295 1.403509 1.370968 1.1355931.157895 1.947368 1.262295 Li₂O + Na₂O + K₂O 0 0 0 0 2.1 4.6 0 TiO₂ +Nb₂O₅ + WO₃ 10.5 10.9 11 9.7 9.6 10.2 10.5 ZrO₂/SiO₂ 1.016393 1.1228070.951613 0.983051 0.982456 1.578947 1.016393 Nb₂O₅/TiO₂ 2.75 2.7586213.4 2.233333 2.2 2.642857 2.75 Total content 100 100 100 100 100 100 100Upper crystallization 1275 1275 1280 1290 1290 1290 1275 temperature °C. Refractive index nd 1.884 1.885 1.882 1.881 1.887 1.881 1.884 Abbenumber vd 39.32 39.22 39.26 39.25 39.24 38.25 39.32 Durability of waterDw 1 1 1 2 1 2 1 Durability of acid D_(A) 1 1 1 2 1 2 1 Density g/cm³5.21 5.16 5.27 5.28 5.26 5.28 5.21 λ₇₀ (nm) 380 380 375 375 375 390 380λ₅ (nm) 340 340 340 340 340 350 340 Extent of striae A A A A A B ABubble content    A₀₀    A₀₀    A₀₀   A₀   A₀    A₀₀    A₀₀

TABLE 9 Embodiment Embodiment Component % 57 58 B₂O₃ 14 14.1 Nb₂O₅ 7.67.5 SiO₂ 6 5.8 ZrO₂ 6 6.1 TiO₂ 2.8 2.7 La₂O₃ 38.2 38.5 Gd₂O₃ 25.4 24Y₂O₃ 0 0 Yb₂O₃ 0 0 Ta₂O₅ 0 0 ZnO 0 0 BaO 0 1.3 CaO 0 0 SrO 0 0 MgO 0 0WO₃ 0 0 Sb₂O₃ 0 0 Li₂O 0 0 Na₂O 0 0 K₂O 0 0 La₂O₃/Gd₂O₃ 1.5039371.604167 La₂O₃ + Gd₂O₃ + Y₂O₃ + Yb₂O₃ 63.6 62.5 Nb₂O₅/SiO₂ 1.2666671.293103 Li₂O + Na₂O + K₂O 0 0 TiO₂ + Nb₂O₅ + WO₃ 10.4 10.2 ZrO₂/SiO₂ 11.051724 Nb₂O₅/TiO₂ 2.714286 2.777778 Total content 100 100 Uppercrystallization 1275 1280 temperature ° C. Refractive index nd 1.8821.883 Abbe number vd 39.25 39.21 Durability of water D_(W) 1 1Durability of acid D_(A) 1 1 Density g/cm³ 5.17 5.18 λ₇₀ (nm) 375 375 λ₅(nm) 335 335 Extent of striae A A Bubble content    A₀₀   A₀

Embodiment of Optical Preform

The optical glass obtained in Embodiment 1 in Table 1 is cut into apredetermined size, and a surface is uniformly coated with a moldrelease agent composed of boron nitride powder, and then it is heated,softened, and press-molded to make preforms of various lenses and prismssuch as a concave meniscus lens, a convex meniscus lens, a biconvexlens, a biconcave lens, a planoconvex lens, and a planoconcave lens.

Embodiment of Optical Element

These preforms obtained in the above embodiment of the optical preformare annealed, fine-adjustment is performed while internal deformation ofthe glass is reduced, so that the optical characteristics such as therefractive index reach desired values.

Subsequently, each preform is ground and polished to manufacture thevarious lenses and prisms such as the concave meniscus lens, the convexmeniscus lens, the biconvex lens, the biconcave lens, the planoconvexlens, and the planoconcave lens. A surface of the obtained opticalelement may also be coated with an anti-reflection film.

The above are only preferred embodiments of the disclosure, and are notintended to limit the disclosure. Various modifications and changes maybe made to the disclosure by those skilled in the art. Anymodifications, equivalent replacements, improvements and the like madewithin spirit and principle of the disclosure should be included in ascope of protection of the disclosure.

What is claimed is:
 1. An optical glass, wherein relative to a totalmass of glass converted by an oxide, and calculated by a mass percentagecontent, the optical glass comprises: B₂O₃: 5˜25%, La₂O₃: 25˜45%, Gd₂O₃:15˜35%, Y₂O₃: 0˜10%, Yb₂O₃: 0˜10%, Nb₂O₅: 2˜15%, SiO₂: 0.5˜15%, ZrO₂:1˜15%, TiO₂: 0.5˜10% and WO₃: 0˜10%, a weight ratio of Nb₂O₅ to TiO₂,i.e., Nb₂O₅/TiO₂, is 2.17˜8.5, and Ta₂O₅ is not comprised.
 2. Theoptical glass according to claim 1, wherein the sum of La₂O₃, Gd₂O₃,Y₂O₃ and Yb₂O₃ is 50˜75%, and the sum of TiO₂, Nb₂O₅ and WO₃ is 1˜20%.3. The optical glass according to claim 1, wherein the optical glassfurther comprises one or more selected from a group consisting of ZnO,BaO, CaO, SrO, MgO, Sb₂O₃, Li₂O, Na₂O and K₂O, and the content is asfollows: ZnO: 0˜15%, BaO: 0˜10%; CaO: 0˜10%; SrO: 0˜10%; MgO: 0˜10%;Sb₂O₃: 0˜1%, the sum of the Li₂O, Na₂O and K₂O is 0˜10%.
 4. The opticalglass according to claim 1, wherein relative to the total mass of theglass converted by the oxide, and calculated by the mass percentagecontent, the optical glass consists of B₂O₃: 5˜25%, SiO₂: 0.5˜15%, ZrO₂:1˜15%, ZnO: 0˜15%, BaO: 0˜10%, CaO: 0˜10%, SrO: 0˜10%, MgO: 0˜10%, thesum of TiO₂, Nb₂O₅ and WO₃ is 1˜20%, the sum of Li₂O, Na₂O and K₂O is0˜1%, Sb₂O₃:0˜1%, and the sum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is 50˜75%.5. The optical glass according to claim 1, wherein relative to the totalmass of the glass converted by the oxide, and calculated by the masspercentage content, the optical glass comprises: B₂O₃: 8˜22%, SiO₂:3˜10%, ZrO₂: 3˜12%, the sum of TiO₂, Nb₂O₅ and WO₃ is 5˜15%, and/or thesum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is 55˜70%.
 6. The optical glassaccording to claim 1, wherein the weight ratio of the Nb₂O₅ to SiO₂ is0.75˜2, preferably 1˜1.5.
 7. The optical glass according to claim 1,wherein a weight ratio of the La₂O₃ to Gd₂O₃, i.e., La₂O₃/Gd₂O₃, is1.28˜1.625, preferably the La₂O₃/Gd₂O₃ is 1.3˜1.6, and more preferably1.4˜1.5.
 8. The optical glass according to claim 1, wherein the opticalglass does not comprise the Y₂O₃ and/or the WO₃.
 9. The optical glassaccording to claim 1, wherein the weight ratio of the ZrO₂ to SiO₂,i.e., ZrO₂/SiO₂,≥1.
 10. The optical glass according to claim 1, whereina upper crystallization temperature of the optical glass is lower than1350° C., preferably lower than 1300° C.
 11. The optical glass accordingto claim 1, wherein a refractive index of the optical glass nd>1.87,preferably nd>1.88; and an Abbe number vd>38.0, preferably vd>39.0. 12.The optical glass according to claim 1, wherein durability of water Dwof the optical glass is above grade 3, preferably above grade 2, morepreferably grade 1; and durability of acid D_(A) is above grade 3,preferably above grade 2, and more preferably grade
 1. 13. The opticalglass according to claim 1, wherein a extent of striae of the opticalglass is above grade C, preferably above grade B, and more preferablygrade A; and a bubble content is above grade A, preferably above gradeA₀, and more preferably grade A₀₀.
 14. The optical glass according toclaim 1, wherein while a transmittance of the optical glass reaches 70%,a corresponding wavelength λ₇₀ is less than or equal to 420 nm,preferably less than or equal to 390 nm; while the glass transmittancereaches 5%, a corresponding wavelength λ₅ is less than or equal to 360nm, preferably less than or equal to 350 nm.
 15. The optical glassaccording to claim 1, wherein a density of the optical glass is lessthan 5.3 g/cm³, preferably less than 5.23 g/cm³.
 16. A glass preform oran optical element, wherein it is made of the optical glass according toclaim
 1. 17. An optical instrument, comprising an optical element,wherein the optical element is the optical element according to claim16.
 18. The optical glass according to claim 2, wherein the opticalglass further comprises one or more selected from a group consisting ofZnO, BaO, CaO, SrO, MgO, Sb₂O₃, Li₂O, Na₂O and K₂O, and the content isas follows: ZnO: 0˜15%, BaO: 0˜10%; CaO: 0˜10%; SrO: 0˜10%; MgO: 0˜10%;Sb₂O₃: 0˜1%, the sum of the Li₂O, Na₂O and K₂O is 0˜10%.
 19. The opticalglass according to claim 2, wherein relative to the total mass of theglass converted by the oxide, and calculated by the mass percentagecontent, the optical glass consists of B₂O₃: 5˜25%, SiO₂: 0.5˜15%, ZrO₂:1˜15%, ZnO: 0˜15%, BaO: 0˜10%, CaO: 0˜10%, SrO: 0˜10%, MgO: 0˜10%, thesum of TiO₂, Nb₂O₅ and WO₃ is 1˜20%, the sum of Li₂O, Na₂O and K₂O is0˜1%, Sb₂O₃:0˜1%, and the sum of La₂O₃, Gd₂O₃, Y₂O₃ and Yb₂O₃ is 50˜75%.20. The optical glass according to claim 2, wherein the weight ratio ofthe Nb₂O₅ to SiO₂ is 0.75˜2, preferably 1˜1.5.